In general, a wind turbine or a wind turbine park is operated with the aim to obtain maximum yield of the capital invested in it, and consequently the wind turbine control systems are configured to maximize the output power, i.e. to operate the wind turbine to capture the maximal power that is available in the wind, with due regard to keeping the wind turbine within operational limits.
While the control system of the wind turbine is designed to take into account the various and varying conditions that a wind turbine operates under, a fault condition may nevertheless arise which requires shutting down the turbine, or alternatively modifying the operation to safe-mode operation. The fault condition may relate to component failure which requires repair or service, or it may relate to conditions which may lead to component failure if the wind turbine is not shut down or operated in safe-mode.
Existing wind turbine shutdown systems are based on measurements of a small subset of the turbine states, such as rotor speed, tower-top acceleration and load measurement to generate a fault signal if the measured value lie outside predefined limits. When shutting down the wind turbine, the fault condition may be taken into account, e.g. by selecting a pre-defined shutdown routine which depends on the nature of the fault. Such shutdown routines are based on the fault scenarios that were taken into account at the design time.
The inventors of the present invention have realized that there is a need for further ways of operating a wind turbine if a fault condition arises during operation of the wind turbine.